MST was developed over a 15-year period by Scott Henggeler and his colleagues at the Family Service Research Center at the Medical University of South Carolina in Charleston. MST is an empirically derived approach to the community-based treatment of high-risk young offenders. It is considered systemic, as it works with the youth's family, friends, and school. It is intensive, short-term, strength based, and solution focused. The skills of a successful MST therapist include an ability to quickly engage with the family, to develop workable short-term goals that require daily effort, and to select goals that are related to the youth's antisocial behavior. The therapist is available 24 hours a day, 7 days a week, and is responsible for creating the conditions for change with the family. Many randomized and quasi-experimental studies document the effectiveness of MST in reducing offending and service use. MST is specifically designed for use with high-risk youth, as defined by the degree of their penetration into the juvenile justice system or by the seriousness of their offenses. The implementation of the MST clinical trials in Ontario, Canada, is a model of policy and program cooperation that is almost as multifaceted as the treatment intervention. Cooperation among two levels of government and multiple agencies in several communities to implement and empirically evaluate this intervention is a rarity in youth justice in Canada. In the spring of 1999, the first data that describe the impact of service on youths seen in the first year will be available. 14 notes